1. Field of the Invention
The present invention relates to a ladder for climbing up to and down from an upper working floor that is set up for a printing press in which press unit is arranged in tiers.
2. Description of the Prior Art
Japanese Patent Laid-Open Nos. 180345/1991, 371835/1992 and Japanese Utility Model Laid-Open No. 56433/1993 disclose working floors for operating a press units at the second and higher floors that are provided for a printing press in which the press unit is arranged in tiers.
The working floor disclosed in Japanese Patent Laid-Open No. 180345/1991 is, as shown in FIG. 1, of a fixed type which is provided outside the press unit. The working floors disclosed in Japanese Patent Laid-Open No. 371835/1992 are of a type that are driven to be elevated or lowered and provided outside the press unit and a fixed type and a bascule type provided outside the press unit. The working floor disclosed in Japanese Utility Model Laid-Open No. 56433/1993 is of a fixed type provided outside the press unit.
There have further been known working floors of a fixed type and bascule type provided inside the press unit arranged in tiers, i.e., provided on the bottom of the lower space, the so called arch, sandwiched by two plate cylinders so as to do work in the arch.
In the above-mentioned conventional working floors, except the working floor of the elevation type disclosed in Japanese Patent Laid-Open No. 371835/1992, a stair case as disclosed in, for example, Japanese Utility Model Laid-Open No. 56433/1993, or a ladder, is provided at a suitable place so as not to hinder workings and walking. In the case of the working floor of a bascule type, a ladder is secured to the working floor of the fixed type that is coupled to the working floor of the bascule type. The workers go up and down using such stair case or ladder.
To install a staircase, as disclosed in Japanese Utility Model Laid-Open No. 56433/1993, at a suitable place that does not hinder the working and walking, generally the place is relatively remote from the press unit. In this case, however, the workers must take a detour to go to the desired working floor making it inconvenient for him to quickly take a measure in an emergency.
To go to and from the working floors of the second and fourth tiers in an arch, in particular, disclosed in Japanese Patent Laid-Open No. 371835/1992 and Japanese Utility Model Laid-Open No. 56433/1993, it is necessary to use a separate ladder or a stepladder and to move and set ladders or stepladders causing the working efficiency to be very low. Furthermore, a fixed ladder, partly closes the front cover that has a function of operating the rotary press and, thus, lacks practicability.
The working floors of the type driven to be elevated and lowered, disclosed in Japanese Patent Laid-Open No. 371835/1992, can be conveniently used. However, the floors themselves are large in scale, manufactured at an increased cost, and further requires an increased running cost for maintaining and checking operation units.